Antimicrobial peptides are a naturally occurring defense system that is widespeard throughout a number of plant and animal species. One type of antimicrobial peptide found in vertebrates is the group of molecules known as defensins. Structurally, these molecules are united by the presence of six invariant cysteines and three intramolecular cystine disulfide bonds. (Lehrer et al., Cell 64: 229-230, 1997; Ann. Rev. Immunol. 11: 105-128, 1993). Two different classes of defensins have been observed. The first are classic defensins, that are stored in neutrophils and macrophages, and which are used to inactivate microbes that these cells have phagocytosed. The second class comprises beta-defensins, which have been isolated from mammalian lung and skin cells. These molecules are known to exhibit a wide range of antibiotic activity against pathogens, such as bacteria, fungi, and viruses (Porter et al., Infect. Immun. 65(6): 2396-2401, 1997).
As noted above, skin cells have been shown to produce beta-defensins. It has also been shown that the exposure of skin cells to bacterial cells, in particular Pseudomonas, even in an inactivated state, can induce the production of beta-defensin-2 in keratinocytes. Presumably this response is present in the skin to protect it from the onslaught of noxious stimuli, particularly in the form of microbes. It has been theorized that the stimulatory components of gram positive bacteria may be lipoteichoic acid or peptidoglycans, while LPS, an endotoxin, is responsible for eliciting the beta-defensin response to gram-negative bacteria.
It would be useful if it were possible to elicit this response at will from the skin with a safer stimulant, so as to provide a consistent protective agent on the skin. To date, however, the use of a safer bacterium than Pseudomonas to elicit skin cell beta-defensins has not been suggested. The present invention now provides a method for stimulating the production of beta-defensins in skin cells with a cosmetically acceptable non-pathogenic bacterium.